Devices that sense sweat and are capable of providing chronological assurance are described. The device (600) uses at least one sensor (620) to measure sweat or its components and to determine a sweat sampling rate. The chronological assurance is determined, at least in part, using the sweat sampling rate. The sweat sampling rate may be determined, at least in part, using a sweat volume (640) and/or a sweat generation rate, both of which may be measured or predetermined.
